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4

Fault code 4 — Out-of-step detection

Rheem · Air Handlers

What does 4 mean?

The system has detected that the compressor is out of sync. This can be due to issues with the compressor itself or the control board.

Common Causes

  • Compressor phase lost
  • Bad control board components
  • Compressor insulation fault

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the compressor wire connections for looseness.

  2. 2

    If connections are secure, consider replacing the control board.

  3. 3

    If the problem persists, the compressor may need replacement.

Browse all codes in this manual (51)
Verified technical data. Last updated: April 2026

Related Faults

1Fault code 1 — Inverter DC voltage overload fault10Fault code 10 — PFC fault (level)11Fault code 11 — PFC power detection of failure
Source: Rheem Air Handlers
Open Manual (Page 186)Search more codes in this manual